Fast neutron reactors cooled with liquid sodium comprise a tank of large dimensions inside which is disposed the reactor core consisting of fuel assemblies immersed in the liquid sodium.
In order to effect the recharging of the reactor core with fuel assemblies, it is necessary to remove the irradiated fuel assemblies from the tank, then to dispose them in a transport cask, generally after a more or less long period of storage during which the radioactivity of these fuel assemblies diminishes, for their evacuation to a reprocessing unit.
Parallel to this evacuation of these irradiated assemblies, new assemblies are introduced into the nuclear reactor in the charging zone of the core where a transfer machine can pick them up to dispose them inside the core in place of the irradiated assemblies.
A transfer machine is therefore available, situated above the core, enabling the assemblies to be removed from or introduced into the core and to be disposed in a storage zone disposed in the reactor tank.
On the other hand, a transfer assembly is available comprising two inclined ramps and a loading-unloading lock which enables the fuel assemblies to be transported between the reactor tank containing the core and a storage zone close to this tank where the assemblies can remain for a more or less extended time during which their radioactivity decreases.
For their passage from the storage zone to the transport cask, the fuel assemblies must be picked up by a complex handling and packaging assembly comprising travelling cranes or other handling machines.
This complex assembly is installed in a part of the reactor specially provided for this purpose, thereby increasing the overall size and the cost of construction of the reactor building.
On the other hand, it is at present being considered, for the installation of fast neutron nuclear reactors, to group a plurality of reactors on one and the same site, so as to facilitate shared use of certain subsidiary installations or items of equipment of these reactors.
In the case of reactors grouped on one and the same site, the device for the transfer and storage of fuel assemblies as described in French Patent Application No. 80-02862 of the NOVATOME company is of great interest because it simplifies considerably the total of the devices necessary for the evacuation of the irradiated assemblies towards a reprocessing factory and for supplying the reactor with new assemblies.
This device comprises, in particular, modules for the transfer and storage of the fuel assemblies, carried by transport vehicles travelling on the site where the reactors are installed.
Nevertheless, in the case where an intermediate storage of the fuel assemblies is necessary after their removal from the reactor tank and before they are picked up by the transfer and storage modules, it is necessary to have available special installations integrated with the building of the reactor for the passage of the fuel assemblies between their storage position in the vicinity of the reactor tank and an evacuation position from which the assemblies can be picked up by the transfer module.